Hex Editing the ISO

**jgrauman** · 07-13-2006, 08:54 PM

Hello,

I would like to add a couple commands to a shell script to be executed on boot. The idea is to be able to make a CD that will do automatic backups so that someone (who knows little to nothing about computers) can put in the CD and boot off of it and it will backup a hard drive.

My basic question is this. I don't want to remaster a CD if I don't have to. All I need is something as simple as
"cp /dev/hda /dev/hdb" in a startup script. I think this could easily be done by hex editing the ISO (if there is room in the startup script for 21 extra bytes or so. 1) Where would I add this?

2) I think it would be very helpful if in a startup script there was an extra 2k or so of comments left specifically for this purpose. That way, if someone wants to have the CD automatically do something, they have 2k set aside to hex edit and they wouldn't have to remaster. Could this suggestion be given to someone in authority who can add this to Knoppix. It only takes 2k or so and is extremely easy to do and adds much functionality in my opinion.

Just add something like the following to the end of the last startup script called:

#add Knoppix startup script code here...
#Knoppix Startup Code Here. Knoppix Startup Code Here. Knoppix Startup Code Here.
#Knoppix Startup Code Here. Knoppix Startup Code Here. Knoppix Startup Code Here.
#Knoppix Startup Code Here. Knoppix Startup Code Here. Knoppix Startup Code Here.
#Knoppix Startup Code Here. Knoppix Startup Code Here. Knoppix Startup Code Here.
...
for a couple thousand bytes.

Josh

**jgrauman** · 07-13-2006, 09:22 PM

I see now that the startup scripts are in a compressed image so I imagine this won't work. Any other ideas?

**malaire** · 07-14-2006, 10:36 AM

Originally Posted by jgrauman

I see now that the startup scripts are in a compressed image so I imagine this won't work. Any other ideas?

If you add a script called "knoppix.sh" to right place (maybe top directory in CD, or the KNOPPIX-directory, I'm not sure) it will be automatically executed when Knoppix starts.
Because such a script doesn't already exists on CD, you can't do that by hexediting the ISO. But you can do it without full remaster as you don't need to fiddle with the compressed image.

**jgrauman** · 07-19-2006, 06:51 PM

Originally Posted by malaire

Originally Posted by jgrauman

I see now that the startup scripts are in a compressed image so I imagine this won't work. Any other ideas?

If you add a script called "knoppix.sh" to right place (maybe top directory in CD, or the KNOPPIX-directory, I'm not sure) it will be automatically executed when Knoppix starts.
Because such a script doesn't already exists on CD, you can't do that by hexediting the ISO. But you can do it without full remaster as you don't need to fiddle with the compressed image.

I think it would be very helpful if this script was put onto the CD, full of 2k of comments like I suggested in my first post. Then you could hexedit the iso. Is there any possibility that this feature could be added. It would only take up 2k of the CD, and would sure make it easier for many people to remaster that only want simple changes. Who should be contacted to suggest this addition?

Thanks.

**Harry Kuhman** · 07-19-2006, 07:25 PM

Originally Posted by jgrauman

I think it would be very helpful if this script was put onto the CD, full of 2k of comments like I suggested ....

I have nothing against the idea, but have you looked at the ISO in it's current state? Have you found the current area that you are talking about? There must be some stuff there now, are you sure that there isn't enough space to do what you want? Do you know if there are not plenty of extra nulls that you could take advantage of? It would be much easier to promote your idea if you could show that you had edited the ISO sucessufully and done something, and now just needed more space to work in to make it generally useful to any more.

**malaire** · 07-20-2006, 08:44 AM

Originally Posted by Harry Kuhman

Originally Posted by jgrauman

I think it would be very helpful if this script was put onto the CD, full of 2k of comments like I suggested ....

I have nothing against the idea, but have you looked at the ISO in it's current state? Have you found the current area that you are talking about? There must be some stuff there now, are you sure that there isn't enough space to do what you want? Do you know if there are not plenty of extra nulls that you could take advantage of? It would be much easier to promote your idea if you could show that you had edited the ISO sucessufully and done something, and now just needed more space to work in to make it generally useful to any more.

I think it's quite different thing to hexedit a file which already exists in ISO, than to add new file to ISO by hexediting it, if that's even possible.

**zemanel** · 08-06-2006, 06:44 PM

Hey... that seems like a crazy idea...but.... why don't you put your script in /etc/rd5.d , it WILL be executed after X starts, it can be more complex cause in most cases the hard drive wont be hda, and it will work and you'll have a lot of less work..

boot from the cd

copy the files and dir's from the dir /KNOPPIX/ to a new directory

chroot for the directory where you copied the /KNOPPIX/ dir

put your sh in /etc/rc5.d from the shell where you chrooted...

make the iso there

burn it on a CD..

& it's done